RotaryEncoder_Library

A C library designed to handle incremental rotary encoders (such as the PEC11R series) using Interrupt-on-Change (IOC) peripherals, quadrature state machine decoding, and a non-blocking debouncing routine for the integrated pushbutton.

Features

• Quadrature Decoding (Gray Code): Processes channels A and B using a software state transition table for maximum accuracy regarding rotation direction (CW Clockwise and CCW Counter-Clockwise).
• Interrupt-on-Change (IOC): Efficient use of the PIC's IOC peripheral on both rising and falling edges, avoiding constant polling in the main loop.
• Integrated Pushbutton Management: Includes a non-blocking state machine with debouncing capable of detecting short clicks and long presses.
• Optional Position Limits: Allows configuring minimum and maximum count boundaries with optional automatic clamping.

Supported / Tested Devices

This library is designed to work with Interrupt-on-Change (IOC) peripherals. The following chips have been explicitly tested and verified:

Microcontroller	Pins	Status	Notes
PIC18F25K83	Pin A -> RB4, Pin B -> RB5 and Pin SW button -> RB3	✔ Fully Tested	The high- and low-priority interrupt vector is used.
Generic PIC16 / PIC18	PORTB pins	⚠ Compatible

Hardware Connection

Typical connection for optimal encoder performance, external pull-up resistors and filtering capacitors are recommended on channels A, B, and the switch (SW) line to mitigate noise and bouncing.

Rotary Encoder Pin	Function	PIC Connection (Example)
A	Channel A (Quadrature Output)	IOC Pin / Digital Input (e.g., RB4 with external pull-up)
B	Channel B (Quadrature Output)	IOC Pin / Digital Input (e.g., RB5 with external pull-up)
C	Common Ground	GND
SW (Switch)	Pushbutton Integrated Switch	Digital Input / IOC Pin (e.g., RB3 with external pull-up)

Usage Example

This example shows how to initialize the rotary encoder, get position and get sw button status.

#include <xc.h>
#include "INTERRUPTManager.h"
#include "RotaryEncoder.h"

void main(void){
    // System and oscillator initialization
    SYSTEM_Initialize();
    
    // Initialize encoder with limits enabled from 0 to 100
    ENCODER_Initialize(0, 100, true);
    
    INTERRUPT_GlobalInterruptEnable();

    int16_t lastPos = -1;

    while(1){
        // Read the current position
        int16_t currentPos = ENCODER_GetPosition();
        if(currentPos != lastPos){
            lastPos = currentPos;
            // Update your display or application logic with currentPos and rotary.direction
        }

        // Periodic button update (every ~5 ms)
        ENCODER_ButtonUpdate_5ms();

        // Process integrated button events
        ButtonEvent_t event = ENCODER_GetButtonEvent();
        if(event == BTN_CLICKED){
            ENCODER_SetPosition(0); // Reset position counter to 0 on click
        }

        __delay_ms(5);
    }
}

Important: handle IOCs within the high-priority interrupt (it can be configured to use low priority or the IVT).

void __interrupt(high_priority) INTERRUPT_InterruptManagerHigh (void)
{
    // Check if Interrupt-On-Change triggered the interrupt
    if (PIE0bits.IOCIE && PIR0bits.IOCIF){
        ENCODER_ISR_Handler();
    }
}

The algorithm on ENCODER_ISR_Handler() evaluates the previous state of pins A and B combined with their current state to compute a 4-bit index expression inside the interrupt service routine:

index = (rotary.state << 2) | currentState

This index looks up a jump table (encoderTable) that determines if the movement corresponds to a clockwise turn (1), counter-clockwise turn (-1), or invalid/noise state (0).

Project Structure

• src/: Core library files (RotaryEncoder.c and RotaryEncoder.h).
• LICENSE: MIT License.
• CHANGELOG: History of updates and bug fixes.

Documentation & Tutorial

For a detailed implementation explanation and step-by-step guide, you can review the following examples:

• https://mrchunckuee.blogspot.com/